In recent years, various technologies have been provided in which a plurality of recording sheets carrying images are stacked to be a sheet bundle, after which cover sheets are attached by adhesive onto said sheet bundle to become a booklet.
For example, there is one technology in which a user stacks a plurality of sheets carrying images to be one sheet bundle, after which the user sets said sheet bundle and the cover sheets onto the bookbinding machine, whereby a booklet is produced by said bookbinding machine.
Further, in a bookbinding system incorporating an image forming apparatus, such as a copy machine and a printer, there is a technology in which a plurality of recording sheets carrying images are automatically stacked to be one sheet bundle, after which a cover sheet is attached onto said sheet bundle by the adhesive. In said bookbinding system, the general procedure to produce a booklet is, firstly, a plurality of recording sheets carrying images are stacked and aligned to become a sheet bundle. After that, adhesive is applied onto the end portion of said sheet bundle. A cover sheet is conveyed to a predetermined position, so that the cover sheet can be adhered to the end portion of the sheet bundle. By the above procedure, the plurality of sheets and the cover sheet are united so that a booklet is produced.
FIGS. 11 (a) and (b) show an example of a booklet which is structured of a sheet bundle and a cover sheet.
FIG. 11(a) shows a status of cover sheet CO which is not yet folded, while FIG. 11(b) shows a status where cover sheet CO has been folded. As shown in FIG. 11(a), a bundle of sheets S, carrying the adhesive on its end portion is moved in an arrowed direction to be adhered to cover sheet CO, after which the sheet bundle is covered with cover sheet CO like a U-shape. In the finished status of booklet MA, edge SE of sheets S is aligned to edge COE of cover sheet CO.
However, after the adhesive is applied onto end portion SB of the sheet bundle, cover sheet CO is adhered to the sheet bundle. Occasionally a problem may occur in which sufficient adhesive force between cover sheet CO and end portion SB cannot be obtained, whereby some sheets S may drop from booklet MA.
One method to overcome this problem is that notches are formed on the edges of sheets S corresponding to end portion SB of the sheet bundle, so that the amount of adhesive to be applied onto end portion SB can be increased, whereby the sufficient adhesive force between sheets S and cover sheet CO is obtained.
In the above-described bookbinding machine, it may be possible to provide a mechanism to form the notches on the end portion of the sheet bundle introduced in said machine, and also in the above-describe bookbinding system, it may be possible to provide a notch forming means along the conveyance route of the sheet carrying images, to form the notches, as described in Unexamined Japanese Patent Application Publication No. 2007-62145.
However, general bookbinding machines tend to be quite large-sized, which incorporate a mechanism to align the sheet bundle which has been set, and said general bookbinding machines will be larger-sized by incorporating the notch forming mechanism, as well as a mechanism to collect sheet chips generated by said notch forming mechanism.
Further, in the bookbinding system of the above-described Patent Document, only the sheets on which images are formed by the image forming apparatus, are notched so that the booklet is produced. Accordingly, said bookbinding system cannot produce a booklet by such procedures that sheets carrying no image are introduced between the sheets on which images have been formed by the image forming apparatus, after which the sheets carrying image and the sheets carrying no image are notched and combined to become a booklet. Yet further, said bookbinding system cannot produce a booklet using only sheets on which no image has been formed by said image forming apparatus. Accordingly if the user is required to produce various kinds of booklets, said bookbinding system cannot be used.